Adsorptive materials such as carbon and other porous materials that act as an adsorptive surface are used to remove a wide variety of organic and inorganic compounds from water, vapor and air. Currently, these materials, once saturated, are disposed of at permitted landfills or returned to a processor that regenerates the material by chemical or thermal treatment. The landfill disposal of the exhausted materials is very expensive as well as environmentally questionable. Current techniques for the regeneration of adsorptive materials include chemical treatments such as acid washing and thermal treatments. These techniques may be used singularly or in combination with each other and are extremely expensive to use.
During the last 5-10 years the technique of using the adsorptive material as a fixed film bed has been developed and patented. The advantages are: lower cost of use of the adsorptive materials; unlimited life of the adsorptive material; and consumption of the contaminant compounds resulting in an environmentally correct approach. With fixed film beds, microorganisms are attached to the absorptive material. The microorganisms on the adsorptive material are contacted with a contaminant containing media for a sufficient period of time to allow the microorganisms to consume the contaminants. In fixed film beds, contaminants are removed from the media by the microorganisms rather than the adsorptive material, as is usually the case. However, the rate of consumption of contaminants by the microorganisms is not as fast as the adsorption rate of contaminants by the adsorptive material when it is used in its usual manner. The general approach to overcome this disadvantage is to increase the retention time of the undesirable compounds with the microorganisms. Two of the drawbacks of the fixed film bed are the extended retention time required for the microorganisms to reduce the contaminant concentration compared to the time required when adsorptive material is used directly and the fact that the microorganisms undergo a starvation period towards the end of the processing cycle during the time when the contaminant level is too low to be nutritionally sufficient for the microorganisms yet still too high to be considered environmentally safe.